The smallest component in small arms ammunition, the percussion primer, is the link between the striking of the firing pin and the separation of the projectile from the cartridge casing. Despite its critical function, percussion primers are the most frequently overlooked and misunderstood cartridge component, probably because of the complexity of the chemical system which they embody. This chemical system is based on a composition which is often referred to as a "priming composition" or "priming mix".
From the original development percussion primers by an American, Joshua Shaw, and an Englishman, Joseph Egg, about 1815, priming compositions have undergone relatively gradual changes. For a period, mercury fulminate was the most commonly used priming composition. In the 1920s, alternate priming mixes were found to replace mercury fulminate, as this latter composition was found to deteriorate too rapidly under tropical conditions. However, the alternate mixes, based on lead thiocyanate/potassium chlorate formulations, were soon recognized as detrimental to weapon barrels because of the formation of corrosive water soluble potassium chloride salts on combustion.
The late 1930s brought a new class of priming compositions which proved to be non-corrosive to small arms barrels: they were based on the primary explosive called lead styphnate, a substance which is much more stable than mercury fulminate. These compositions are still in use today. However, they suffer from the undesirable creation of airborne particles containing lead and other heavy metals. Government regulations are increasingly being imposed on firearms training procedures based on concern for the potential injurious effects on individual health of such metals.
Except for the first primer using pure mercury fulminate as an igniter, all other common priming compositions are chemical mixtures of, at least, a primary explosive, an oxidizing compound and a fuel source. To these are generally added other ingredients such as sensitizers and binders. The three main ingredients are essential to meet the input (sensitivity) and the output (ignition) requirements for a given primer. A typical primer based on lead styphnate would, for example, commonly incorporate barium nitrate as an oxidizer and antimony sulphide as a fuel and friction producing agent as well as aluminum, another fuel, and tetracene, a sensitizer.
The challenge of reducing the potential deleterious effects of priming compositions on individual health is not an easy one to meet. The replacement of toxic ingredients contained in the current compositions, essentially heavy metal compounds, must be effected without impairing performance. Thus, alternate compositions must have a level of sensitivity similar to that of lead styphnate primers, a temperature stability at least equivalent to that of the current composition and must produce neither environmentally undesirable nor corrosive by-products.
In the past ten years, many researchers have been working to find non-toxic or less-toxic priming compositions but the available prior art all show some significant drawbacks. For example, U.S. Patent No. 4,581,082 to Hagel et al, as well as U.S. Patent No. 4,608,102 to Krampen et al, both correctly addressed the problem of the toxicity of the combustion by-products but their primers have one idiosyncrasy: they tend to deteriorate upon exposure to high temperatures. Another solution provided in U.S. Patent No. 4,963,201 by Bjerke et al is one of a primer composition with environmentally acceptable by-products, free of toxic compounds. But the Bjerke composition demands a critical and difficult preparation procedure in order to accommodate the mixing problems associated with the use of strontium nitrate as the oxidizer.
Accordingly, a principal object of the present invention is to provide a primer composition for use in small arms and other forms of ammunition that has similar or improved characteristics compared to current lead styphnate priming compositions without producing toxic emanations containing lead, barium, antimony or other heavy metals.
It is also an objective to provide a primer composition that is thermally stable.
Another object is to provide a non-corrosive mix to prevent premature corrosion of barrels upon firing.
A further object is to identify a primer composition that is easily adaptable to existing, regular processes for production methods of small arms primers, that is, a solution that would not require further manufacturing steps or inconveniences compared to production of current lead styphnate primers.
Still another objective of the present invention is to provide a solution which will not adversely affect primer costs.
The invention herein in its general form, will now be summarized, and then its implementation in the form of specific embodiments will be detailed with reference to the tables following hereafter. These embodiments are intended to demonstrate the principle of the invention, and the manner of its implementation. As such they are merely exemplary. The invention will then be further described, and defined, in its most general and more specific forms by means of the series of claims which conclude this Specification.